Reinforced soldered-seam metal sheathed cable



H j w 2 1 m w y ,fw f 7 t wh Mw 1, n m0500200 0:2550 y 5/ 0 .91. w W e@n 5. W mmnmwm /w J 4 2 n 0.5120022 5h50 5023 m40 It; S0520 fr@ f2 m u205.502. m23. mada 00223222702@ /M w A m 2 mm M, An A v, 2 m 5 2 n n m mv m A E E e a m m25 0.29m 2w 0 5&00 IJ. ...u c m m2000520 w .25.2 E020 nn 325m 5.3252620.. E C um uns; 0.23m 2m 0 5&00 1 Y m oct. 24, 195o FiledNOV 20, 1945 Oct. 24, 1950 c. J. BEAVER ETA. 2,527,172

REINFORCED soLDERED-SEAM METAL smmn CABLE Filed Nov. 20, 1945 2Sheets-Shoot 2 l5 /5 gf l F/Ga 6 F/GS Patented Oei. 24, 1950 REINFORCEDSOLDEBED-SIAM METAL SHEATHED CABLE Charles James Beaver, Bowden, andEdward Leslie Davey, Timperley, England, mignon to W. T. Glover &Company Limited, Manchester, Lancashire, England, a British companyApplication November 20, 1945, Serial No. 629,808 In Great BritainNovember 24, 1944 2 Claims.

This invention relates to electric cables of the kind which, when inservice, work with a substantial difference of pressure between theinside and outside of the sheath which covers the dielectric of a coreor of a group of cores. the pressure difference being due to theapplication of fluid under high pressure inside the sheath. Theinvention is particularly applicable for use with the Glover highpressure gas-filled cable (see the Journal of the Institution ofElectrical Engineers, volume 91, part II, page 35 and U. S. PatentSpecification No. 2,067,169).

The invention is concerned with the improved construction of the part ofthe cable immediately surrounding the dielectric. In this improvedconstruction the sheath is replaced by an envelope made from thin metaltape which is formed to shape by running it longitudinally on the core(or group of cores) bending it transversely to enclose the core and toform flanges, lying side by side and projecting radially where the edgesof the curved portion of the tape meet, joining these flanges, bysoldering, and bending the united flanges over so as to lie upon orclose to the exterior of the adjacent wall of the envelope and thenbinding the envelope with reinforcing metal tape applied helically withshort lay, with or without a layer of bedding between it and the sheath.The metal tape envelope takes the place of the usual lead sheath withsubstantial advantages. It can be made of only a few mils thickness,whereas a lead sheath is of the order of 100 mils in thickness.

The tape used for the envelope is preferably of soft copper, but brassor other suitable strong, soft metal may be used. For the reinforcement,metals such as hard brass. steel, phosphor bronze or cadmium copper maybe used. In addition to serving their normal function as reinforcement,

they assist the envelope by retaining the flangey in its positionagainst the wall of the envelope. In this position the soldered jointbetween the flanges is nearly wholly in shear and the shear stress maybe reduced to a desirable low value by giving an appropriatecircumferential width to the flanges.

Owing to the differences in the mechanical' properties of the metaltapes used for the envelope and for the reinforcement, it can beprovided that the greater part of the load due to the pressure iscarried by the reinforcing tapes so that the stress in the envelope canbe kept low.

To enable the invention to be more fully understood and readily carriedout a description of a preferred form of construction and of its methodof manufacture will now be given by way ci' example and with the aid ofthe accompanying diagrammatic drawings wherein:

Figure 1 is a perspective view of the stepped end of a gas-filled cablewith a pressure retaining envelope constructed in accordance with theinvention,

Figure 2 is a side elevation of a machine for manufacturing the envelopeof the cable shown in Figure 1,

Figure 3 is a plan of the machine shown in Figure 2, and

Figures 4, 5, 6, 7, 8 and 9 are cross-sectional views taken on the linesIV-IV, V--V. VI-VI, VII-VII, VIII--VIIL and IX-IX, respectively ofFigure 2 and on an enlarged scale as compared with Figures 2 and 3,showing successive stages of the manufacture of the envelope.

As will be seen from Figure 1 of the drawings the cable comprises astranded conductor i, of

which the surface has been smoothed somewhat as by drawing through adie, and a dielectric 2 built up of pre-impregnated paper tapes. Overthe dielectric is a conductive screen 3 which in turn is surrounded by alayer of copper woven fabric tape 4 by which is meant a woven fabrictape in which are incorporated a number of fine copper wire warps 4a.This is enclosed in an envelope li formed by applying a flat striplongitudinally to the outside of the core and folding it round to fltthe core and to leave two flanges t which are secured by a illm ofsolder 'i and are bent to lie against the envelope 5, by a method to bedescribed. Surrounding this metal envelope is a layer 8 of copperV wovenfabric tape similar to the tape l and serving as a bedding for areinforcing metal tape l applied helically with a short lay. Over thereinforcement layer is a protective sheath or covering iii.

The preferred method of manufacturing the envelope l will now beexplained. The ,cable core il consisting of conductor I, dielectric 2.conductive screen 3 and copper woven fabric tape 4 is drawn through aguide l2 and over a grooved roll il. Above the roll i3 is a reel Ilcarrying a fiat coil of thin metal tape i5. This tape is drawn on' thecoil and passed under a cylindrical roller II with a flange il at eachend which holds it in contact with the top surface of the core in theposition shown in Figure 4, which is a crosssection on the line IV--IVof Figure 2. From the rolls I3 and I6 the core il and strip I5 are drawnthrough a second pair of rolls, the lower roll i8 of which is in theform of a disc with a grooved periphery of approximately semi-circularshape. The upper roll i! has in its periphery a circumferential grooveu-shaped section, the walls of which fold the tape i5 into the form ofan inverted U-shaped channel of which the semicylindrical part lies inengagement with the upperhali'ofthecore ",auhowninl'igun.

3 On leaving the rolls I8 and I9 the core and the tape are drawn throughanother set of rolls comprising a roll 20 with a semi-circular groovewhich holds the tape I5 in contact with the upper half of the core I Iand a pair of side rolls 2 I which bend the sides of the invertedchannel into engagement with the lower half of the surface of the coreand the margins of the tape into flanges 6 which lie close to each otherand extend vertically downwards below the core, as shown in Figure 6.Preferably the inner surfaces of these flanges are tinned, the tinningoperation being performed before the tape is applied to the core. Asthey leave the rolls 20 and 2I, the flanges are passed through a bath 22containing a non-corrosive iiux, for example a mixture of rosin(colophony) and rosin oil, and then through a bath 23 containing moltensolder. The solder used should preferably be one having a melting pointabove 200 C., so that there is a suitable margin between its meltingpoint and the melting point of the metal used during the installation ofthe finished cable for making a plumbed joint between the envelope andsome other part such as the gland of a joint box or termination. Anexample of a suitable solder is one consisting of 56% tin and 44% lead,and when this solder is used, the bath will be held at a temperature ofapproximately 280 C. On leaving the solder bath 23 the core I I and itsenvelope 5 pass through three more groups of rolls. The first groupconsists of an upper roll 24 with a peripheral groove of semi-circularcross-section and a pair of side rolls 25 with transversely curvedsurfaces which engage the two lower quadrants of the envelope and withcylindrical surfaces which squeeze the soldered joint down to athickness which will result in the joint having an optimum shearstrength. This thickness will depend mainly on the temperature of thesolder in the bath and to a lesser extent on the type of solder used(see British Non-Ferrous Metals Research Associations Research MonographNo. 1 entitled Tin Solders by S. J. Nightingale and O. F. Hudson). Withthe example of solder given above the optimum joint thickness is 0.004inch. The following group of rolls consists of an upper grooved roll 26and a single side roll 2l which engages a lower quadrant of the envelopeand presses the jointed flanges through an angle of about 45 as shown inFigure 8. The third set consists of a pair of grooved rolls 28 and 29which press the jointed flanges still further so that they lie alongsidethe surface of the envelope as shown in Figure 9. After passing througha guide 30 the metal tape enveloped core is given its binding ofreinforcing metal tape, preferably after applying a layer of bedding tothe envelope.

The presence of the layer of copper woven fabric l over the screen 3surrounding the dielectric 2 (see Figure 1) serves to prevent theenvelope from being caused to adhere to the screen II when the solderedjoint is being made. In cases where the dielectric contains freeimpregnating compound, this layer, or alternatively a cover stripextending longitudinally on the core so as to lie between the joint andthe core, will also serve to prevent the free compound from running intothe space between the flanges before they are united and thus fromcontaminating the surfaces before they have been soldered together.

It will be appreciated that by the improved method of gas-imperviousenvelope for the core,

` a considerable saving of metal results and that,

owing to the reduction in circumference, this is accompanied by a smallsaving in the parts which surround the envelope. At the same time thereis obtained an envelope with a much higher fatigue limit than a leadsheath.

What we claim as our invention is:

1. A high tension power cable comprising a pressure-resistant,gas-impervious covering enclosing an insulated electric conductorcharged 'with gas under superatmospheric pressure, said coveringcomprising a longitudinally seamed sheet metal envelope havingoverlapping longiwhich the other overlies the outer surface of thefolded edge. solder uniting the contiguous surfaces of the longitudinaledges and means for holding the soldered seam in a position where thestress exerted on it by the gas pressure to which the envelope issubjected is substantially wholly a shear stress, said means comprisinga helical lapping of short lay of reinforcing metal tape surroundingsaid envelope and retaining the soldered edges in position against thewall of the envelope.

2. A high tension power cable comprising a pressure-resistant,gas-impervious covering enclosing an insulated electric conductorcharged with gas under superatmospheric pressure, said coveringcomprising a longitudinally seamed sheet metal envelope havingoverlapping longitudinal edges of which one is folded back and liesagainst the outer wall of the envelopeand of which the other overliesthe outer surface of the folded edge and a thin film of solder extendingover substantially the whole outer surface of the folded back edge anduniting substantially the whole of said surface to the contiguoussurface of the overlying edge, and means for holding the soldered seamin a position where the stress exerted on it by the gas pressure towhich the envelope is subjected is substantially a shear stress, saidmeans comprising a helical lapping of short lay of reinforcing metaltape surrounding said envelope and retaining the soldered edges inposition against the wall of the envelope.

CHARLES JAMES BEAVER.. EDWARD LESLIE DAVEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Y Date OTHER REFERENCES Sil-Fos and Easy-Flo,Bulletin No. 12, page 5, published by Handy and Harman, 82 Fulton Bt.,

New York, N. Y., 113-112 Lit.

